Limited access to fasteners is a common problem in many industries. In the aerospace industry, the problem of limited access to fasteners may be more pronounced due to more stringent engineering requirements and the tighter space constraints generally associated with aerospace structures. For example, aircraft commonly include hydraulic systems which including tubing sections that may be joined using flare nuts that are threadably engaged to in-line fittings. In order to provide leak-proof connection between the flare nut and the fittings, it is necessary to tighten the flare nuts to relatively high torque values. In addition, it is typically necessary to verify the torque values to which the flare nuts are tightened by using a torque wrench.
Because of the high torque levels that must be applied to flare nuts, it is desirable to use a wrench that provides a large amount of contact area between the wrench head and the flare nut. Typically, flare nuts have a hexagonal shape with six sides or flats adjoined at a corresponding number of corners. A wrench that applies rotational force to the flats of the flare nut may minimize the risk of damage to the corners which may otherwise become rounded if the wrench slips off of the flats during tightening of the flare nut. Certain wrenches such as socket wrenches and box end wrenches are configured to engage the flats of the flare nut. However, engagement of a socket wrench or a box end wrench to the flare nut requires access from the top or bottom of the flare nut which may not be possible due to the mounting of the flare nut on the tubing section.
Conventional open end wrenches allow for side engagement of the wrench to a fastener such as a flare nut. The wrench head of an open end wrench typically includes a pair of jaws having opposing parallel faces which are spaced at a distance to match the width of the flare nut measured across the flats. Ideally, the jaws are spaced to provide a generally snug or sliding fit with the flare nut such that rotational force from the wrench is applied to the flats instead of to the corners. However, manufacturing tolerances in the wrench and/or in the flare nut may result in a jaw spacing that may be greater than the width across the flats which may result in rounding off of the corners of the flare nut when large rotational force is applied to the flare nut.
Flare nut wrenches are a type of open end wrench that also allow for side engagement of a flare nut. Flare nut wrenches include a wrench head that is configured similar to a box end wrench with the exception that the wrench head includes a cutout on one side to allow the flare nut wrench to be slipped over a tubing section. Once the flare nut is slipped over the tubing section, the flare nut wrench may then be moved axially into engagement with the flats of the flare nut so that rotational force may be applied. Unfortunately, the cutout in the wrench head allows for the spreading apart of the wrench head when large rotational force is applied to the flare nut. Such spreading apart may result in slippage of the wrench head which may result in rounding off of the corners of the flare nut.
Limited rotational space is another challenge associated with fastener installations in confined spaces. In this regard, structure that is located adjacent to a fastener installation may limit the ability to rotate the fastener to the extent necessary to allow for progressive rotation of the fastener. For example, structure that is in close proximity to a flare nut installed on tubing may limit the ability to rotate the flare nut using conventional wrenches. In this regard, the adjacent structure may limit the repeated progressive rotation of the fastener to the extent necessary to tighten or loosen the fastener. Repeated progressive rotation of a fastener comprises engaging a wrench to one pair of flats of the fastener, rotating the fastener, disengaging the wrench head from the fastener, and then re-engaging the wrench to a different pair of flats to continue the rotation of the fastener in the same direction. Repeated progressive rotation of a six-sided flare nut using a conventional (i.e., non-offset) open end wrench requires a swing angle of no less then 60 degrees. In this regard, flare nut installations where adjacent structure limits rotation to less than 60 degrees would prevent rotation of the flare nut using conventional tools.
A further challenge associated with certain fastener installations is a requirement to maintain the wrench at a fixed orientation relative to a centerline or axis of the fastener. For example, when torquing a fastener to a desired torque level, it may be desirable to maintain the wrench at a perpendicular orientation relative to the fastener axis in order to provide an accurate indication of the level of torque that is being applied with a torque wrench. In this regard, certain industries restrict the use of torque wrenches where it is possible for the wrench head to engage the fastener in an off-axis or non-perpendicular orientation. Because conventional open end wrenches allow for off-axis orientation of the wrench head relative to the fastener, the use of open end torque wrenches may be limited.
As can be seen, there exists a need in the art for a wrench that permits side engagement of a fastener and which facilitates fastener rotation in locations having limited rotational space. Furthermore, there exists a need in the art for a wrench that facilitates repeated progressive rotation of fasteners within a minimal swing angle. Additionally, there exists a need in the art for a wrench wherein the wrench head is maintained in a perpendicular orientation relative to the fastener centerline. Finally, there exists a need in the art for a wrench having the above-described attributes and which is also of simple construction and of low cost.